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United States Patent | 5,532,987 |
Fujita ,   et al. | July 2, 1996 |
A focus error detecting device includes a reflected beam obscurer and a two-division photodetector. The observer obscures a part of the reflected beam. The two-division photodetector includes first and second light receiving sections separated from each other by a division band region which receive the reflected light beam not obscured by the obscurer. A focus error signal is produced based on the output of each light receiving section. Each light receiving section has an array of tapered projections along its edge in the division band region. Alteratively, the light receiving sections have a main part with an edge coincident with an edge of the division band region, and groups of light receiving stripes extending in a direction parallel with the edges of the main part.
Inventors: | Fujita; Teruo (Nagaokakyo, JP); Karaki; Morihiro (Nagaokakyo, JP); Irie; Mitsuru (Nagaokakyo, JP); Nakane; Kazuhiko (Amagasaki, JP) |
Assignee: | Mitsubishi Denki Kabushiki Kaisha (Tokyo, JP) |
Appl. No.: | 427811 |
Filed: | April 26, 1995 |
Aug 20, 1992[JP] | 4-221318 | |
Aug 24, 1992[JP] | 4-223912 | |
Nov 30, 1992[JP] | 4-319885 | |
Apr 28, 1993[JP] | 5-102613 | |
May 31, 1993[JP] | 5-128894 | |
May 31, 1993[JP] | 5-128895 | |
Aug 17, 1993[JP] | 5-203460 |
Current U.S. Class: | 369/44.24; 369/44.42; 369/120 |
Intern'l Class: | G11B 007/09 |
Field of Search: | 369/44.12,44.23-44.24,44.41-44.42,54,112,120 250/201.5 |
Re33548 | Mar., 1991 | Kime | 369/44. |
4079248 | Mar., 1978 | Lehureau et al. | |
5161139 | Nov., 1992 | Inoue et al. | 369/44. |
5173890 | Dec., 1992 | Miyake et al. | 369/44. |
5270996 | Dec., 1993 | Ono | 369/44. |
Foreign Patent Documents | |||
59-223953 | Dec., 1984 | JP. | |
59-223954 | Dec., 1984 | JP. | |
61-94246 | May., 1986 | JP. | |
63-131333 | Jun., 1988 | JP. | |
63-53618 | Oct., 1988 | JP. | |
3-70859 | Nov., 1991 | JP. | |
4-243021 | Aug., 1992 | JP. |
Bouwhuis, "Principles of Optical Disk System", Adam Hilger (1985), pp. 77-79. Irie, "Focus Sensing Characteristics of the Pupil Obscuration Method for Continuously Grooved Disks", Proc. Int. Symp. on Optical Memory, 1987, Japanese Journal of Applied Physics, vol. 26 (1987), Supplement 26-4, pp. 183-186. |